It is known to prepare an aqueous solution of dichlorohydrins e.g., 2,3 dichloro-1-propanol and 1,3 dichloro-1-propanol, herein collectively dichlorohydrin, by reacting in a reaction zone allyl chloride, water and chlorine in dilute aqueous phase.
U.S. Pat. No. 2,714,121, incorporated herein by reference, discloses producing halohydrins by using high dilution of e.g., 250 to 400 volumes of water per volume of e.g., a halosubstituted hydrocarbon in aqueous medium with subsequent addition of the halogen, and keeping the organic by-product phase dispersed as fine particles.
U.S. Pat. No. 2,714,123, incorporated herein by reference, discloses producing an aqueous solution of dichlorohydrin in a series of reaction zones wherein substantially all of the water is fed to the first of the reaction zones and the other reactants added in substantially equimolar proportions into each of the other reaction zones.
U.S. Pat. No. 3,909,382 discloses recovering acid values, such as hydrochloric acid formed during olefin chlorohydrination, by series flow through a plurality of electrodialysis stages to upgrade the acid to higher concentration.
From Japanese Pat. No. 74,00369 it is known that the product mixture from the reaction of a lower olefin, chlorine and water can be electrodialyzed to remove the by-product ions of hydrogen and chlorine, and the ion-depleted chlorohydrin solution circulated to the single reaction zone, enabling the production of a concentrated aqueous chlorohydrin solution.
A disadvantage of the known processes is that substantial amounts of water are used in the reaction zone of the process to obtan higher selectivity, that is the yield of the desired chlorohydrin product, based upon the chemical feed. Such conventional processes result in a substantial volume of aqueous effluent containing minor amounts e.g., 1000 to 2000 parts per million by weight (ppmn) of organic impurities. Such effluent requires energy intensive treatment to reduce the amount of organic materials to low levels acceptable to be passed to receiving bodies of water such as rivers, lakes and the like. The present invention provides a method for both improving selectivity to the desired dichlorohydrin product and enabling reduction in the amount of aqueous effluent, thereby effecting great energy savings for the overall process.